The invention relates to six-axis force/torque transducers.
So-called six-axis force/torque transducers are used to measure the following six possible loads occurring at a single point: X axis force, Y axis force, Z axis force, X axis moment, Y axis moment, and Z axis moment, based on Cartsian coordinates. An application for these transducers is in robot wrists. An important aspect of any multi-axis force/torque transducer, especially one mounted in a robot wrist, is the ability to measure forces which are applied at a distance from the transducer. Any distance from the transducer to the point of force application creates a moment arm and can produce large torques on the transducer. Therefore, a force sensitive sensor must be able to measure small forces with high resolution, and at the same time withstand and measure large moments, without distorting the force measuring ability.
Multi-axis force/torque transducers typically have two rigid members through which the load to be measured is applied. Flexural beams are connected between the rigid members so as to deform (e.g., strain) in response to a load applied between the two rigid members. Deflection sensors (e.g., strain gauges) are mounted to sense deformations of the flexural beams and thus the load between the rigid members.
Two general approaches used in prior multi-axis force/torque transducers are single-stage transducers and multiple-stage transducers In a single-stage transducer, there are only two rigid members and a set of flexural beams between the two. On the flexural beams are a plurality of strain gauges that react to loads on more than one axis, though each in an independent, linear manner. The strain gauge outputs are transformed via matrices to obtain the loads on each axis. In a multiple-stage transducer, there are a plurality of stages that each employ a pair of rigid members and connecting flexural beams, each stage deflecting primarily under one axis of loading, with minimal deflection under loads from other axes. Strain gauges of each stage correspond to the load under which their stage deflects and are said to be "decoupled" with respect to loads on other axes.